This achievement seems superhuman, but just how out-of-the-ordinary is Phelps?
To find out, we can turn to a simple law of statistics. This basic math shows that Phelps' gold-medal count is so sky-high, it wouldn't have been predicted to occur, at least not for another 250 years. [The Science of Olympic Rivalries: Do Adversaries Help or Hurt?]
In the natural world, it has long been recognized that phenomena that vary over a wide range of values follow a remarkably simple pattern. Considering the size of earthquakes, for example, we know that there are numerous small temblors every day, with larger quakes being increasingly rare. Similarly, the size of meteor strikes, terrorist attacks and even the popularity of different websites follow a pattern where the biggest numbers rapidly become increasingly scarce. The amazing thing about these seemingly random events is that their rarity or frequency follows what is known as a power law distribution, a simple mathematical form that gives a straight line graph when plotted in a certain way. Even the popularity of words used in the English language follows such a "rule."